linux-kernel - Re: [PATCH] mmc: sdhci-msm: Add sdhci

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Message-ID: <df2a5586-0cd3-d744-d490-fa24c7e385a3@linaro.org>
Date:   Mon, 28 Nov 2016 17:51:05 +0200
From:   Georgi Djakov <georgi.djakov@...aro.org>
To:     Ritesh Harjani <riteshh@...eaurora.org>, adrian.hunter@...el.com,
        ulf.hansson@...aro.org
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] mmc: sdhci-msm: Add sdhci_reset() implementation

On 11/24/2016 06:06 PM, Ritesh Harjani wrote:
> Hi Georgi,
>
> I collected some info on this problem. May be below info might help you.
>
> I think "Reset 0x1" problem is occurring because of below call stack.
> SDHCI_RESET_ALL to SDHCI_SOFTWARE_RESET register will anyway trigger the
> sdhci_msm_pwr_irq.
>
> But I think the problem is that the above occurs in spinlock context
> and because of only one core the IRQ will never be serviced, hence you
> were seeing (Reset 0x1) error.
>

Hi Ritesh,
Thanks for looking into this. So yes, its called in spinlock context and 
what we need to do is just handle the power irq after writing to reset 
register.

[..]
>
> To prove above I tried this and the problem goes away. But I still dont
> think that the below approach is correct. As it will still trigger a
> pwr_irq as well.
>
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 62aedf1..01e611c 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -174,6 +174,8 @@ void sdhci_reset(struct sdhci_host *host, u8 mask)
>                 /* Reset-all turns off SD Bus Power */
>                 if (host->quirks2 & SDHCI_QUIRK2_CARD_ON_NEEDS_BUS_ON)
>                         sdhci_runtime_pm_bus_off(host);
> +               if (host->ops->voltage_switch)
> +                       host->ops->voltage_switch(host);
>         }
>

Yes, our own reset() function that additionally handles the irq will work.

Thanks,
Georgi